Hands-free, sometimes referred to as touch-free, dispensers are well known in the art. Many dispensers are battery powered which allows them to be conveniently placed most anywhere without connection to electrical service. Of course, batteries, also referred to as cells, run down over a period of time and this requires that the batteries be replaced. If a battery is not timely replaced then the dispenser is rendered inoperative. One way to overcome this problem is to replace the battery on a predetermined schedule. However, this is considered wasteful as the full life of the replaced battery is not used.
An alternative solution is to provide a battery backup system for the dispenser. In such a configuration, the dispenser switches to a second charged battery when the first-used battery is fully or partially discharged. Although an improvement, use of a battery in the last stages of its life can also be problematic. Specifically, the power levels provided by the almost depleted battery may not be adequate to fully operate the dispensing system, motor and/or pump that is used to dispense the fluid material. Accordingly, there may be dispensing cycles that last longer than are supposed to or the dispensing cycle may be intermittent. Another drawback of using multiple batteries requires that they be connected in series. As such, a controller associated with the dispenser chooses a battery with the highest voltage value to operate the device. This has the disadvantage of requiring batteries to be of the same type. When connected in series, the performance of a set of batteries is limited by the weakest cell. As such, mixing the different types of batteries (in series) can cause failure. Once one of the batteries discharges, it can start to charge in the opposite polarity and result in failure of the battery and possibly even the dispenser. In the past, attempts to differentiate battery types in a series configuration result in a difficult and complicated circuit. Therefore, there is a need for a hands-free or touch-free dispenser with a battery backup system that fully depletes one battery before switching over to a second battery. There is also a need to ensure that a full operational cycle is implemented regardless of the remaining charge value. And, there is a need to allow for different types of batteries to be used in the dispenser. There is also a need in the art to provide an indication as to which battery is fully depleted so that it can be replaced.